In a total knee arthroplasty (TKA) procedure, a patient's distal femur is resected and replaced with a prosthetic femoral implant, and the patient's proximal tibia is resected and replaced with a prosthetic tibial implant. The prosthetic femoral implant articulates with the prosthetic tibial implant to restore joint motion.
Many factors influence joint motion after the TKA procedure. The size and shape of each prosthetic implant will impact joint motion. Additionally, the location and orientation of each prosthetic implant, which is determined by the location and orientation of the corresponding bone resections, will impact joint motion. The tension or laxity of the surrounding soft tissue will also impact joint motion. For example, if the surrounding collateral ligaments are too tense, joint motion may be limited, but if the surrounding collateral ligaments are too lax, improper femoral rotation or femoral lift-off may occur. Also, the soft tissue balance around the joint will impact joint motion.
Different surgical philosophies have traditionally influenced TKA instruments and procedures. For example, a first, “measured resection” philosophy emphasizes bone resections while preserving the natural joint axis and soft tissue. A second, “soft tissue balancing” philosophy emphasizes soft tissue modifications while preserving bone.